1. Field of the Invention
This invention is directed to a device for coupling together the sections of a multi-section seismic marine streamer cable, such as might be found in classes 181/.5 and 340/7R.
2. Description of the Prior Art
A detailed description of the construction and use of seismic streamer cables was presented in the above-referenced co-pending patent application Ser. No. 069,208. Nevertheless, for completeness, a brief overview of prior-art seismic cables will be presented.
A typical seismic marine streamer cable may be two miles or more long and is customarily towed behind a ship along a proposed line of survey. The streamer cable is made up of a number of sections that may be 200 to 300 feet long so that fifty or so sections make up the complete streamer cable. Contained within the streamer cable are a plurality of hydrophones for detecting seismic waves. The hydrophones are grouped together to form separate, individual data channels. There may be more than 300 such data channels. Since each data channel requires two conductors to transmit seismic signals to a signal utilization device, 600 or more separate wires are contained within the streamer cable along with the hydrophones.
Since the entire streamer cable is composed of a plurality of separate sections, means must be provided to couple the sections together mechanically and electrically. A number of different varieties of streamer couplers are known. One venerable type of coupler is shown in FIGS. 1 and 1a of U.S. Pat. No. 3,376,948 to Morrow. In FIG. 4 of the same patent, Morrow illustrates an improved design employing a cylindrical multiconductor pin-and-socket electrical plug and a screw-type mechanical coupler. One particular objection to Morrow's multiconductor plug is that, for a cylindrical plug of manageable size, having a diameter less than about 2.5 to 3 inches, only about 100 wires can be accommodated. Furthermore, the entire coupler must be completely disassembled from an associated streamer section to repair broken wires.
Another coupler assembly is shown in FIG. 3 of U.S. Pat. No. 3,812,455. Here, a two-part assembly is provided that is bolted together. Inside the assembly, a recess is provided for three elongate male and female plugs to which the wires are soldered. Here again, the number of wires that can be accomodated is limited. Although the wiring is reasonably accessible, the plugs cannot be inspected after mating because the connector plugs are mated at the same time that the two halves of the coupler are assembled.
Other typical streamer cables are described in U.S. Pat. No. 2,465,696 to Paslay, U.S. Pat. No. 3,290,645 to Pavey Jr. et al and U.S. Pat. No. 4,092,629 to Siems et al.
The streamer cable coupler disclosed in the above referenced co-pending application Ser. No. 069,208 now U.S. Pat. No. 4,260,211 consists of a two-part, hollow, quick-disconnect fitting having an internal diameter sufficient to contain a multicontact connector plate for electrically interconnecting the signal wires from two adjacent streamer sections. The two-part fitting includes male and female parts. The parts are lockable together by locking balls mounted in the female part that fit into detents around the circumference of the male part when the two parts are mated together. A locking ring holds the balls in place after assembly.
The coupler as disclosed in my copending application was an improvement over the earlier known couplers in that the ball-and-detent locking mechanism permitted easy assembly and disassembly of the coupler. When the male and female parts are separated from one another, the connector plates and wiring were completely exposed for servicing. An indefinite number of wires could be accommodated because more connector plugs could be provided simply by lengthening the connector plate and, if necessary, by lengthening the female housing as well.
Despite its advantages over earlier couplers, the need for certain improvements soon became apparent. When the two parts of the housing were separated so that the plug-wiring on the connector plate could be serviced, the only mechanical attachment between two adjacent cable sections was the wiring itself. In the field, aboard a rocking ship at sea, it was difficult to keep the adjacent sections from being pulled apart during servicing.
A considerable amount of slack in the conductors was required so that the connector plate could be fully withdrawn from the female housing. When the coupler housings were reassembled, it was necessary to double back and stuff the wires into the female housing and around the connector plate. With several hundred wires involved, there was danger that one or more wires would be pinched or broken during the reassembly process.
Finally, because one part of the two-part coupler was male and the other part female, a pair of cable sections could be assembled in only one way, that is one cable section could not be turned end-for-end with respect to the other cable section. The cable sections were effectively polarized. Indeed, all known cable sections used in present-day marine seismic operations suffer from that same disadvantage.
A ball-and-detent quick-disconnect electrical connector is disclosed in U.S. Pat. No. 3,964,771. Like all other known connectors, that connector is polarized, i.e. it is made up of a male and a female part. Additionally, to service the internal conductors and the pins and sockets, the entire assembly must be completely taken apart.